Mosquitoes are largely to blame for spreading West Nile virus, which starts when the critters become infected by feeding on infected birds. "Infected mosquitoes then spread West Nile virus to people and other animals by biting them,” according to the Center for Disease Control and Prevention (CDC).

Most people who are infected do not experience symptoms, the CDC warns. However, a small percentage of people — roughly 1 in 5 — develop a fever and may additionally experience headaches, body aches, vomiting, diarrhea, or a rash, among other signs of the virus.

M. Norman Oliver, the state health commissioner, said the virus-spreading mosquitoes can possibly infect residents through the end of October.

In the meantime, Oliver recommended Virginians take precautionary measures, such as using insect repellant, wearing long-sleeved shirts, and removing standing water from birdbaths and planters — places which serve as a breeding ground for mosquitoes.